The caution comes despite polls released this week showing voters think Republicans are more fit to handle most of the country’s pressing issues and that the GOP holds an “unprecedented” lead over Democrats in a new Gallup Poll asking voters for their generic party preference. Meanwhile, President Obama’s job-approval rating is below 50 percent in most surveys and the popularity of his signature new health care law dipped again in August.

Political analyst and college professor Larry Sabato on Thursday became the latest forecaster to predict sweeping GOP gains this fall, saying his model now sees Republicans retaking the House, close to capturing the Senate, and poised to pick up a large number of governorships as well.

But Paul Lindsay, spokesman for the National Republican Congressional Committee, cautioned that “the fact that analysts now consider that goal a possibility doesn’t change the challenge ahead of us.”

Michael Steel, spokesman for House Minority Leader John A. Boehner, said the path to capturing the House remains a “steep climb.”

“We’ve got a lot of hard work to do, and no one is taking anything for granted,” he said.

And the spokesman for Senate Minority Leader Mitch McConnell, Kentucky Republican, simply noted that his boss “has not made any such predictions,” when he was asked about Republican chances to retake the Senate.

If history is any guide, the approach former Notre Dame football coach Lou Holtz took - predicting his Fighting Irish were the underdogs, no matter who they were playing - works well in politics.

In 2005, when Republicans controlled the Senate, then-Democratic Minority Leader Sen. Harry Reid predicted on the chamber floor that it would take “a miracle” for his party to win the five seats needed to gain control in the 2006 elections. But with then-President George W. Bush and the Iraq war weighing the Republicans down, that’s exactly what happened.

Democrats are also quick to remind Republicans that the 2010 votes have yet to be counted, and that every campaign develops its own dynamics.

Democratic National Committee spokesman Hari Sevugan said the trend that the GOP should be paying attention to is the fact that, “despite a favorable national environment, they aren’t doing as well as they should be in many individual races, including Senate races in Nevada, Kentucky, Connecticut and Alaska, to name just a few.”

A number of Republican primaries have already sparked bitter internal fights and winning candidates who did not have the blessing of either the state or national party establishment, Democrats say.

“The consequence of allowing the ‘tea party’ to take over the Republican Party is a slate of deeply flawed candidates who are allowing each of these races to be a choice, rather than a reflection of the national mood,” Mr. Sevugan said.

Maryland Rep. Chris Van Hollen, who chairs the Democratic Congressional Campaign Committee, argued that Republican enthusiasm in the polls and primaries so far this year will also boost Democratic enthusiasm and turnout in November.

“The mistake that [Republicans] are making is to conclude that by the end of the day you will not have a strong Democratic turnout,” he told reporters last week while flatly predicting his party would retain control of the House.

But recent polls are only feeding a growing sense of GOP excitement about their chances this fall.

A Gallup Poll released on Wednesday found that voters were more confident in the ability of Republicans to handle seven of nine major issues listed, including terrorism, immigration, federal spending and the Afghan war. The poll followed another Gallup survey on Monday that gave the GOP a 10 percentage point edge over Democrats on a “generic” ballot and a 25 percentage point lead in overall voter enthusiasm.

Perhaps most surprising was a poll released Tuesday by the firm Public Policy Polling (PPP) that charted the growing distaste of voters in the swing state of Ohio for Mr. Obama and his agenda. By a 50 percent to 42 percent margin, Ohioans said they would rather have Mr. Bush back in the White House rather than Mr. Obama.

These could be bad omens for Democrats who went into the August recess hoping their legislative accomplishments would slow the GOP momentum before the November election.

But with the Labor Day start of the fall campaign approaching, the polls say that attempts to rewrite the political narrative have largely failed and that health care reform, federal stimulus spending and financial-regulation overhaul are being drowned out by worries related to unemployment and the economy.

“Somehow the [Democratic] Party base needs to get reinvigorated over the next two months, or there’s going to be a very, very steep price to pay,” said PPP Director Tom Jensen said in an analysis of his firm’s recent polls.

Isaac Wood, of the University of Virginia’s Center for Politics, agreed.

“I don’t think the GOP needs to be worried about peaking too early,” he said. “The drumbeat of bad news for Obama and his allies has energized Republicans and demoralized Democrats.”

With turnout in midterm elections traditionally around 40 percent, compared with 60 percent in presidential years, Mr. Wood said, the party that can best get its voters to the polls holds a distinct edge. “That enthusiasm advantage should be firmly on [the GOP‘s] side,” he said.

The situation leaves some wondering whether the Democrats’ best strategy right now is hoping the Republicans implode.

“Fortunately for Democrats, we’re up against Republicans,” said Christopher Kofinis, a Democratic strategist. “They still have no message, the [Republican National Committee] is a disaster, and a GOP civil war has created openings in key Senate and governor’sOE races. The challenge is to exploit these key weaknesses and create a better national narrative for voters.”